Dual-layer to flange welded joints are used in a variety of applications, including heat transfer applications. For example, air gap-insulated double-walled exhaust manifolds have been increasingly used in exhaust systems of motor vehicles. Together with other air gap-insulated double-walled exhaust pipes, they provide for the optimal operation of emission control devices, such as catalytic converters, positioned downstream. Further, they increase the durability of the exhaust manifold and reduce noise, vibration and harshness.
Air gap-insulated, double-walled exhaust manifolds also reduce the amount of heat released from the exhaust gas to the environment, so that the exhaust gas flows to the emission control device at a higher temperature than in single-walled exhaust manifolds and exhaust pipes. This is significant especially during the warm-up phase of the internal combustion engine, because the catalyst will thus rapidly reach its working temperature. In addition, the air gap insulates the outer wall from the inner wall, thereby minimizing discoloration and excessive heating of the outer wall. This is becoming more important as turbo charging, direct injection, Homogeneous Charge Compression Ignition, and other technologies produce higher temperatures, pressures, and loads on exhaust systems.
Prior-art dual-walled exhaust manifolds have an outer wall and a one-part or multipart inner wall, which may be shaped parts made of sheet metal in a half-shell design. During assembly of the manifold, the inner and outer walls are connected to an exit flange. Currently, such connections require both external and internal welds. Therefore, such a manufacturing process is expensive and can lead to several problems.
For example, internal welds are difficult to perform and inspect, increasing the likelihood of weld failure as well as labor costs. Deficiencies in these welds can lead to decreased durability, improper insulation, wall warping and deformation, decreased emissions performance, discoloration, as well as increased noise and vibration. In addition, while techniques such as TIG and Plasma welding help avoid weld spattering and wall warping or deformation, these techniques are expensive, and still require labor and inspection.
Accordingly, manufacturing costs of a manifold assembly can be significant, and a continual need exists in the industry to reduce these costs. Reducing the number of welds in a manifold assembly can significantly reduce such costs. In addition, the placement and type of the welds impact the design options as well as the overall strength and durability of the manifold assembly.
Therefore, there is a need in the art to provide a dual-layer to flange welded joint that can overcome at least several of the above disadvantages and achieve at least some of the above advances desirable in the art.